Oscillatory compressor



Nov. 22, 1960 R. R. HULL OSCILLATORY COMPRESSOR 2 Sheets-Sheet 1 Filed May 14, 1957 m N0 m R N E m R ATTOR/V'X R. R. HULL 2,961,149 OSCILLATORY COMPRESSOR Nov. 22, 1960 Filed May 14, 1957 2 Sheets-Sheet 2 l 88 as 3 INVENTOR.

\ Rad-ER? R, HULL ATTOR/VEK OS CILLATORY COMPRESSOR Robert R. Hull, Pasadena, Calif., assignor to Richard G. Markham, Solvang, Calif.

Filed May 14, 1957, Ser. No. 658,988

27 Claims. (Cl. 230-55) This invention relates to compressors and more specifically it relates to a small oscillatory compressor of a type which is specially suitable for use with aquariums.

An object of this invention is to provide an oscillatory compressor to serve as an air pump which is especially eflicient and reliable and which, with minimum power consumption will supply continuously an abundant supply of low pressure air for a long time without interruption for maintenance or repair. An allied object is to provide a construction for such a pump which is quiet, safe, attractive and relatively inexpensive,

Another object of this invention is to provide a compression chamber which is especially suitable for relatively short stroke oscillatory operation of the type, for example, which is provided by an armature and an electro-magnet actuated by an alternating current in which volumetric eificiency is excellent, and in which the means which seal between the relatively moving parts of a compression chamber do not rub with resultant abrasion, and yet do not suck in or billow out appreciably as a result of suction and compression cycles.

A further object is to provide a sealing means which minimally interferes with the intended and desirable functioning of other components of the compressor, and in which several hundred millions cycles of operation may be expected before maintenance or repair is needed.

Still another object of this invention is to provide a compressor wherein an inexpensive, simple, positive, and automatic means adjusts the gap between an electromagnet and an armature oscillated thereby so that the energy supplied by these components to an associated compression means may in accordance with the wishes and intent of the designer using the principles of this invention, be made to increase, remain the same, or decrease as the back pressure against the compressor changes in either direction from a reference point as a result of changed conditions of use or otherwise. This is a very esirable feature in a device intended for use where back pressure conditions may vary from almost zero to several pounds per square inch, and where manually adjustments are a bother and are seldom properly made.

Still another object of this invention is to provide a compressor construction in which the energy normally expended in useless and objectionable vibration is conserved and is made to do useful Work, and more specifically to provide a compressor wherein those components which are already present are so disposed, arranged and supported, as to cause these components themselves to counterbalance each others unbalanced forces of a vibratory nature.

Still another object of this invention is to provide a construction which supports and positions the compressor mechanism in such a way that, while providing sulficient supply and positioning for normally operation and for normal handling and shipping, still does not transmit any appreciable vibratory tendency to the place of attachment of the supporting means while the pump is in operation.

A related object of this invention is to provide an en- "ice closure which provides a suitable place of attachment for a compressor mechanism constructed and isolated as above stated, and additionally efiiciently damps those vibrations which are undesirably conveyed through the support positioning components of the compression mechanism.

According to this invention, alternating or interrupted direct current impressed upon an electro-magnet causes an armature which is adjacent thereto and spaced therefrom to actuate a compression chamber type compressor, thereby compressing air or some other fluid which is conducted by suitable means therefrom to an outlet connection from which it may be further conducted to a place of use.

According to a preferred but optional form of this invention the compression chamber has a cup-shaped part fixed to an armature plate so as to be oscillated thereby. An opposedly positioned plunger extends into the cupshaped part. The plunger is immovably attached to a structure which itself is attached immovably to the electro-magnet. Between the wall of the cup-shaped part and the outside of the plunger, a suitable flexible seal which miniminally interferes with the normal positions of these parts, is secured so that it does not slide or rub on either part. Inlet and outlet valves are incorporated in the cup and plunger, respectively, so as to permit fluid to be drawn into said chamber, compressed therein and expelled therein.

The armature, together with the movable parts of the compression chamber, is positioned suitably in relation to the poles of the electro-magnet by means of armature positioning springs. In operation the electro-magnet pulls the armature toward itself during the power-on cycle, and the armature positioning springs cause the armature to move in the opposite direction during the power-off cycle. Air, or any other desired working fluid provided to the compressor is compressed in the compression chamber as a result of the above relative movement of the cup and plunger.

The above and other features of this invention will be fully understood from the following detailed description and the accompanying drawings, of which:

Fig. l is an elevation partly in cross-section of the presently preferred embodiment of the invention;

Figs. 2 and 3 are fragmentary cross sections taken at line 22 and 33 respectively of Fig. 1; and

Figs. 4-8 inclusive are enlarged views of various components of the compressor of Fig. 1.

In Fig. 1 the presently preferred embodiment of an oscillatory compressor assembly 19 according to this invention is shown. Because of the complexity of this assembly it will be discussed in two primary divisions, the first division consisting of the enclosure components, and the second division consisting of the compressor mechanism, of which there are two principal sub-divisions, these sub-divisions being an electro-magnet means and a compression means. Theenclosure components will be described first.

The enclosure assembly comprises the following components arranged in the manner hereinafter described. An outer container 12 is secured by an interference fit to its closure plug 13 which in turn has cemented to it feet 14 which are approximately equally spaced, and are positioned against its outside surface adjacent to rim 15.

An inner container 16 having a closure lid 17 is fixed almost rigidly within the outer container by sand fill 18, which sand fill consists of sand such as clean aquarium sand, which is lightly tamped into inter-container space 19 between the two containers. This sand can be coated with a suitable oil, rosin, or the like, to aid in removing dust carried by the air passing therethrough, and also for removing electrostatic charges. The closure sliding fit.

An eyelet passes through hole 21 punched in the wall of inner container 16. The eyelet is secured in this hole by crimping. At a'position inside the inner container and diametrically opposed to the eyeletthere is secured by means such as cementing a shipping bumper 22. p

A drop cord 23 passes through a hole 24 provided for the purpose in the wall of the. outer container and is secured in said hole by wire fastener 25. After passing through the inter-container sand fill, the drop cord passes through a hole 26 provided for that purpose in the closure lid 17 of the inner container, and is secured therein by a wire fastener 27, which also passes through the lid. Two support spring fastening rivets 28 pass through holes punched therefor in the closure lid of the inner container, and are secured therein by suitable means such as soldering.

An air connection tube 29 passes through hole 30 provided therefor in the wall of outer container, and is secured in this hole by soldering. A flexible-air conduit tube 31 fastens by an interference fit and cementing to the inner end of the air connection tube 29 and from this connection, inside the outer container, the tube passes through the inter-container sand fill and through the Wall of the inner container by way of the hole in eyelet 2i), and is secured within the inner container by means of an interference fit and cementing to an air discharge tube 32 which connects to the compression mechanism to be described below.

A reinforcing spring 33 is secured within the flexible air conduit tube 31 by an interference fit at the end thereof which is adjacent to air discharge tube 32. This spring extends through the flexible air conduit tube for a distance suflicient to prevent kinking of the tube at its passage through the wall of the inner container, by supporting the wall of the tube from inside.

A mufller string 34 is secured by being looped through the reinforcing spring 33 and is contained within the walls of the flexible air conduit tube 31. The string is doubled, both for the purpose of holding it in the tube by attachment to the spring, and for the purpose of sufiiciently filling the tube for best muffling of sound.

Wire nuts 35 fasten leads 36 and 37 to their respective connection point with the wires of the drop-cord 23 within the inner container.

The oscillatory compressor of this invention is encased by the above components in a sound deadening and vibration damping double-walled enclosure. Several additional elements are provided for said enclosure in addition to those described above. For example, an outer covering 38 which may desirably be of a suitable thick paint or plastic sheet such as plastic wall paper, covers the outer container (except for the plug and bottom) thereby enhancing the appearance of the assembly, providing a protective covering, and damning vibration of the metal of the outer container 12 which might otherwise produce noise by being vibrated by small but troublesome compressor-produced forces which are not completely counterbalanced, isolated or damped by the other components of the enclosure. A plaster fill 39, which preferably is rounded at its edges and preferably made slightly crowned at its center, enhances the appearance of the assembly, reduces fire hazard, and prevents vibration of the outer end of the container 12 which might result without the presence of this plaster fill, especially when the inter container sand filled has tamped a little because of vibrations which have reached from the compressor mechanism in spite of the isolation and damping means to be described below.

The outer container provides an inexpensive, fire resistant, and suitably shaped outer wall for the enclosure assembly. This container may conveniently comprise a quart size, single flange type food can, modified by two'- punched holes, 24 and 30. The drop cord passes through hole 24, and connection tube 29 passes through hole 30.

The closure plug 13 closes the open end of the outer container 12 and provides a place for attaching the feet 14. This closure is known as a plug for a single flange quart size food container. The support feet 14 serve to space and isolate the air pump assembly from its Supporting surface and from any other structure associated with the said supporting surface. This minimizes the vibration-induced noise and additionally minimizes disturbance to fish in adjacent aquariums. These feet, made of suitable resilient material such as medium density sponge rubber, are attached in a uniformly spaced manner adjacent to the rim of closure plug 13 by means of a suitable cement, for example, rubber cement.

The inner container 16 provides an inexpensive fire resistant inside Wall for the enclosure assembly 11, and thereby affords a compartment for the compressor mechanism 40 within this enclosure. This container is preferably a dog-food type can modified by shortening it by cutting off part of the wall, and by punching hole 21 for the passage of eyelet 2i). Eyelet 20 passes through a hole in the inner container, and is secured therein by crimping. The evelet thereby provides a smooth edge, for the hole so that the flexible air conduit 21 which passes therethrough will not be damaged by the wall of the inner container.

Shipping bumper 22 is inoperative during normal compressor use. It restrains the compressor mechanism 40 within the compartment formed by the inner container and the inner container cover when for any reason, as for example in shapping, excessive motion might other wise result with conseouent damage to the compressor sub-assembly or its enclosure. This bumper is made of a suitable resilient material of suitable size, a convenient example being a medium density sponge rubber one-half inch thick and an inch in diameter, which is secured by cementing to the inside wall of the inner container adjacent to the bottom of the inner container at a place on the container wall that is diametrically opposite the eyelet 20.

The inner container closure lid 17 slides snugly over the open end of the inner container, thereby closing this end against entry to the inter-container of foreign materail such as sand, and additionally provides a place for attachment of the support and positioning components for the compressor mechanism 40. This is a special lid which is modified by hole 26 to pass the drop cord, and by holes 41 to accommodate the support spring fastening rivets 28, see Fig. 3.

Support spring fastening rivets 28 secured in holes 21 in the inner container cover provide a place for attachment of support means for the compressor mechanism.

ese rivets conveniently have an end section 0.10 inch long by 0.12 inch diameter, a threaded center section which is 0.18 inch long, with 7 national coarse thread, and another end section 0.18 inch long and 0.20 inch in diameter which is used in riveting.

The inter-container sand fill 18 maintains the inner container and its enclosed mechanism in an approximately central position within the outer container and thereby provides an inexpensive means for accomplishing this placement. Additionally, this sand fill, especially when suitably treated as by coating with oil, contributes greatly to extended trouble free valve operation by providing a large area, low-velocity filter for air entering the compressor mechanism. Also the sand fill provides weight and thereby enables the enclosure to serve as a suitable anchor for the entire assembly and its associated support and positioning components. Furthermore, because the particles of said move upon each other when the fill is vibrated, such a fill by reason of the friction thereby introduced, provides an excellent damper for attenuation of the small but unavoidable vibration which is transmitted from the compressor mechanism through its supporting means to the supporting enclosure. The inter-container sand fill also acts as a sound deadener, and this is a highly desirable feature for a pump which is intended to be operated in quiet living rooms. For such living room usage it is also desirable that a compressor of this type be substantially fire proof, and this sand fill also serves that function.

Air connection tube 29 provides a place within the outer container for attachment of the outer end of flexible air conduit tube 31 and provides a passage for conducting air through the wall of the outer container. It also provides a place for the user to connect another tube to the compressor assembly for the purpose of conducting air compressed by the compressor mechanism to the place of use. This air connection tube is preferably inch outside diameter, about 24 gauge with a length about 78 inch. It is preferably rounded slightly on both its ends and is secured within the punched hole 30 in the outer container by means of solder.

Within the inner container and beneath the cover, compressor mechanism 4i} is supported and positioned by a pair of support springs 42 and 42a as shown in Fig. 3 which attach at one of their ends to the inner container's closure lid 17 by being screwed snugly upon the threads of the support spring fastening rivets 28, and which have their other ends attached to members of another pair of support spring fastening rivet 42 which are attached to a portion of the compressor mechanism to be described below. These support springs are made of 0.035 inch diameter music wire, wound 16 turns per inch, right hand thread, with a free length inch. Between 2 and 2 /2 turns of the said springs are fixed to the securing means at each end. The internal diameter of these springs is such that they screw snugly upon a 7 inch national coarse thread.

The flexible air conduit tube 31 provides an air passage to conduct the air between the compressor mechanism 40, air discharge tube 32, and the air connection tube 29. Additionally, this tube 31 provides within itself an elongated compartment wherein the mufller string is contained. This air conduit tube, in order to provide additional distance of air travel for muffling purposes is made longer than that which would be necessary merely to connect the two tubes to which it is attached. The flexible air conduit 31 is preferably made of vinyl tubing 0.156 inch inside diameter with 0.038 inch wall thickness. it has a length of approximately 14 to 20 inches, with 18 inches being the preferred length.

The muffler string 34, contained as it is within the flexible air conduit tube 31, provides a mufiler for deadening the sound produced by air compression and by the valve action. Without such mufller means, these sounds would travel outwardly through the flexible air conduit tube 31 in objectionable volume. This string is a soft cotton type of such diameter that the two strands will fill about twothirds of the internal cross section area of the flexible air conduit tube. It is preferably about 16 inches long, being 32 inches of string doubled.

The re-inforcing spring 33 prevents short kinking of the fiexibe air conduit tube 31 adjacent to the eyelet 2t and additionally provides a place for attaching the mother string which, were it not so restrained, could be blown out the tube 31. This spring is about 0.15 inch outer diameter and about 2 inches long and may conveniently be made of 0.035 inch diameter music wire.

The drop cord connects the compressor mechanism with a suitable source of electric power. It may be made of No. 18 POT type about 6 feet in length. The wire fasteners which anchor the drop cord to the container ma conveniently be Heyco fasteners.

The above completes the description of the enclosure assemblies which enclose the compressor mechanism. The compressor mechanism will now be further described and will be understood to consists of all of the structure within the inner container which is supported by the support springs 42 and 42a.

The compressor mechanism 40 includes as one of its sub-divisions an electro-magnet sub-assembly 44 which sub-assembly includes a yoke shaped frame 45 providing a pair of arms 46, 47 as may best be seen in Fig. 3. An electro-magnet core 48 is held between the arms by means of rivet 49 which passes through holes 50. The core 48 is composed of laminations 51, which laminations consist of iron plates which are generally E shaped. A bobbin 52 which may be made of nylon, for example, is immovably secured to the electro-magnet core by an interfcrence fit on the center projection of the core. A winding 53 is wound on to the bobbin and is secured against self abrasion by means of baking varnish thereon. This winding is terminated at each end by lead wires 36 and 37, which are attached to the wires of the drop cord 23.

Tabs 56 and 57 are formed, one in each arm. These tabs may conveniently be produced by die-punching them from the arms so that the tabs are integral with the said frame 45. Spring fastening rivets 58, 59 are immovably secured to said tabs by means such as heading. Support springs 42, 42a are secured to support spring fastening rivets 58, 59 respectively, by having several end turns thereon snugly screwed on to the aforesaid rivets. At their other end they are similarly turned on to support spring fastening rivets 28 so as to support the compressor mechanism 40 from the closure lid 17 of the inner container 16.

The frame 45 provides a connecting and securing member by means of which the compressor mechanism 40 is held in assembled relationship within the inner container. This frame provides a place for attachment of other subassemblies to be further described below. The frame, including its integral tabs and arms may conveniently bepress-formed from inch by 1% inch cold rolled steel.

The laminations 51 provide a suitable electro-magnet core. Additionally, they provide a means for securing the bobbin and the magnet wire which is wound thereon in an immovable manner in relation to the frame. Steel rivet 49 secures the laminations into one integral sub-assembly. This rivet may conveniently be Mr inch diameter by one inch length, round head. The bobbin serves as a supporting form and as an insulator for the winding 53, and for the device shown has a center opening to receive a A; by /s inch central projection of the laminated core. The magnet wire itself serves to convert electricity impressed thereon into magnetic flux and this wire may conveniently be size 34 formvar insulated copper wire. The lead wires 36 and 37 connect the ends of the winding to the end of the drop cord wires, and may conveniently be insulated No. 18 size stranded copper wire.

The compressor mechanism also includes as its other subdivision a compression means which includes an armature 63 and a compression chamber means 62 as shown in Fig. 1. The armature 63 comprises a base plate 64, a center plate 65, and a back plate 66, which are immovably secured in relation to each other by fourspring fastening rivets 67 which pass through holes 68 in said plates as shown in Figs. 1 and 2. These rivets are secured to said plates by heading. There is immovably positioned in relation to the above three plates, a cupshaped compression chamber element 69 which is secured by solder to one side of the back plate 66. An inlet valve retainer 70 is secured by soldering within the cup-shaped compression chamber element 69. This cupshaped compression chamber element 69 is the cup member of a cup and plunger device to be described. A felt filter 71 and a fine mesh screen 72 are confined laterally within the wall of a hole 73 intended for this purpose in the center plate 65. These are confined axially in said hole by the armature base plate 64 on one side and by the cup-shaped compression chamber element 69 on the other side.

Bumpers 74' pass through holes 75 provided therefor in the .armature base plate 64,. and are thereby laterally positioned. The enlarged heads of these bumpers occupy spaces provided by holes 76 intended for that purpose in the center plate 65. The enlarged heads on these bumpers are axially restrained between the base plate and the back plate. a a

A valve disc 77 occupies space provided therefor between thevalve seat portion of the cup-shaped compression chamber element 69 and the inlet valve retainer 7 5, as shown. in Fig. 4, and is retained by these parts a manner which, with-the mechanism at rest, causes the valve disc to. almost contact or to press very lightly against a valve seat 78. The armature 63, thecup-shaped compression chamber element 69, the rivets and bumpers, the felt filter and the screen together make up an armature assembly which moves in response to forces exerted by the electro-magnet.

A cylindrically shaped compression chamber element hereinafter called a plunger 83 is secured immovably to a pair of anchor plates 79 by screws 84 at the time the device is assembled. The anchor plates 79 are at the same time secured immovably to the yoke shaped frame by means of these same screws.

A plenum space 86 is provided in the plunger and this space includes a counterbore 87 which construction provides a .shelf 88 as shown in Fig. 8. A valve retainer spring 89 which is held within the plenum space 86 by the walls of the counterbore holds a discharge valve retainer 90 tightly in place against the shelf 38, and is itself retained in a somewhat compressed condition by a closure plug 91 as shown in Fig. 1. The closure plug 91, in addition to retaining the discharge valve retainer spring 89, serves to close the open end of the plenum space in an air-tight manner. A compressor mechanism air discharge tube 32 is secured by'a press fit and cementing in a hole provided for this purpose in the sides of the plunger '83.

A compression chamber seal ring 93 makes an air-tight fit with the inside wall of the cup. The cup is provided with a shoulder 95 and a lip 96, and the seal ring fits between them. In addition to this restraint, the seal ring makes a tight interference fit with the said cup wall, and is cemented thereto. A snap ring 160 is fitted in said ring, and exerts a radial force near the membrane, or web section of the said ring. The outer, peripheral wall of the ring and the inner wall of the cup are firmly fixed relative to each other in this manner, and there is no sliding movement between them. i

The plunger 83 has at'its end nearest the electromagnet a ring-shaped neck which terminates at a shoulder 98 and has a lip 99 at its' upper end. See Fig. 8. The inner wall of the compression chamber seal ring makes an interference fit on this neck, and is also cemented thereto. The cemented interference fit, together with the shoulder and lip provide an air-tight joint between the seal ring and the plunger, in which there is no sliding movement between the seal ring and the plunger. Anchor plates 79 receive spring fastening rivets 80. Four armature positioning springs 81 are snugly threaded upon the threaded part of spring fastening rivets 67 (which rivets also serve to hold the armature plates together and also upon the threaded part of the rivets 80. The armature assembly is thereby positioned and elastically connected to the anchor plates, which are in turn attached to yoke shaped frame 45.

The attachment of the spring fastening rivet Sil to the anchor plate 79 is made by riveting the end of the aforesaid rivets which is intended for that purpose within holes 82 in the anchor plate. This means of attaching the spring fastening rivets to the anchor plate permits them to be attached thereto while the springs are also applied thereon. This type of application is needed because the springs will necessarily have been attached prior to the final riveting. V

The sealing ring 93. and its features will now be more fully described. Most desirably a compression chamber for usein an air compressor should have no internal air space remaining at. the completion of the compression cycle, because such an air space is unswept by compression elements, thereby reducing the capacity of the compression chamber and also reducing the efficiency of the compressor as a whole. In a compressor built in accordance with this invention, only a small volume of the compression chamber remains unswept, because the plunger and the seal ring 93 approach very closely adjacent surfaces of the cup and the valve retainer. The usual arrangement of a U-ring is reversed in this device so that the fieXible portion of the seal. ring is adjacent to the inner surface .of the cup and the valve retainer. In this way, the volume enclosed between the. legs is outside the compression chamber.

Also most desirably, the sealing means which permits the relative motion between the relativeiy movable parts of the compression chamber and at the same time prevents escape of the air or gas which is being compressed, should require no energy to perform its functions, and also it should not increase the residual (unswept) volume of the compression chamber at the end of the compression cycle. Neither should it decrease the volume of the compression chamber at the end of the intake cycle by reason of its being flexible or for any other reason. Neither should it interfere with any desirable relative positioning of the other parts of the compression chamber which it seals, nor should it deteriorate because of abrasion. Seals for relatively long stroke compression chambers, which are the most common type of chamber, are usually of the sliding type. In connection with small size, low pressure compressors, such seals dissipate in friction a disproportionately large part of the total power consumed by the device. Also, no sliding seal which has been devised thus far for this purpose has proved to be durable over long term operation. In this invention, by using a short stroke and the particular sealing means showman almost perfect seal has been attained.

Constructions which utilize short stroke compression means and which are sealed by diaphragms overcome the above problems to some extent. However, diaphragm seals tend to suck-in and to billow out during the intake and the compression cycle respectively, and thereby tend to reduce the efliciency of the compressor in which they are used.

To keep the volumetric efficiency of the compressor at a reasonable level, diaphragms need to be quite thick and taut. However, when the diaphragm is thick and taut it has an appreciable effect upon the oscillator excursion of the parts it connects. With set and resultant loosening of the diaphragm which comes with its aging, volumetric efficiency decreases, but even more troublesome perhaps is the fact that the length of travel of the connected members relative to each other, can thereby change, and this change produces striking and clattering of associated components such as armatures and electromagnets if no adjustment for this is made, or unless undesirably excessive clearance are originally provided in the compressor.

In my invention, all of the above problems have been virtually eliminated by using the seal ring shown in the drawings. Instead of a sliding seal, a specially shaped U-section seal ring 93 is provided with the open part of the U facing away from, and placed outside of the compression chamber. This increases the volumetric efiiciency. The seal is fixed by its peripheral wall in an immovable and airtight manner to the inside wall of the cup and is fixed by its inner wall in an immovable and airtight manner to the outside of the'plunger. Since these and the only places of contact, are .immovably secured relative to the object which they contact, there is no sliding action and there is therefore no resultant wear or abrasion of the ring.

As can be seen from an examination of Fig. 7, where the seal ring is shown in its uncompressed condition, the legs of the U are wider at their free ends, so that an angle of 18 is included between them. A flexible web section 161 joins the two legs. This web has its thinnest portion at its center third. The inner and outer threads taper at an angle of about to become wider adjacent the legs. The thinner center third is between about 0.018 and 0.025 inch thick, depending on the material used. The inner and outer walls of the seal ring are also slightly tapered when the ring is free. These walls are held parallel when the seal is installed.

The compression chamber seal U ring 93 as incorporated in a compressor built according to this invention,

has its inner and outer wall positioned relatively more.

closely together after assembly than they are before being secured and restrained within the compression means. That is to say, that the two walls are relatively compressed toward each other, by forcing outwardly the inner wall by reason of its interference fit with the plunger and by' forcing inwardly the peripheral wall by interference fit in the cup. In addition to being positioned closely together after assembly, these walls of the compression chamber seal ring 93 are tipped inwardly toward each other at the unconnected or open part thereof by about 9 degrees, which is the amount of outward flare moulded into these walls at the time the ring is made. The result of the closing together of the walls and of the angular changes of the walls and the non-uniform thickness of the flexible seal U section 191 is to provide a ring which has an overcenter action as its inner and outer walls are moved axially in relation to each other during compressor operation. Also, motior is distributed over the web section for longer flex life. In a ring of this type, it will be found that when the inner and outer wall are axially in line, the flexible section 101 has a tendency to shift the said walls axially relative to each other one way or the other. This occurs at what may be called the center point of a normal stroke. When the walls are axially displaced relative to each other a little on either side of the center, there is a point where there is no particular inherent tendency for such motion. Upon further axial shifting which requires some energy to accomplish, there is a tendency for the two walls to return toward the central normal position.

It is important to note that this flexible seal section 161 is of a comparatively short radial dimension, particularly compared to the thickness of the two leg section of the U-shape and that there is a negligible tendency of this section to billow or suck in during the compression or intake cycles respectively.

Such a seal when properly proportioned and when used in a suitable mating compression chamber members such as the cup and plunger shown, has a relatively long range of axial excursion between its inner wall and peripheral wall before it interferes with the relative motion of these parts by reaching the end of this non-interfering excursion. in practical construction these end positions of interference are beyond the end positions of the intended relative travel of the compression chamber components and therefore do not interfere at all. Thus the seal as shown may assume for all practical purposes the positions in travel throughout the excursions which they would assume if sealed by a freely sliding seal. The over-center action of the mid-point of the excursion results from the construction which provides the above explained long excursion without interference at the end points within the oscillatory range desired, while providing a construction free from other objectionable features.

Since the overcenter action is at or near the midpoint of travel it does not interfere with the action of the seal 10 when the armature is at the end of its excursion in either direction, and such energy as might be substracted by action of the seal at one end of the excursion is recovered almost in its entirety on the other side as it goes over center.

The armature base plate 64 is the primary magnetic member of the armature 63 and provides most of the magnetic interaction of the armature with the electro-magnet. The base plate along with the center and back plates, provides weight in the armature assembly for storing and releasing energy required for proper compressor operation. The base plate provides a positioning and securing means for the bumpers 74 and for the spring fastening rivets 67. Also a hole 102 in the base plate provides an air passage for air on its way to the compression chamber, while the plate area around and adjacent to this hole retains the felt filter 71 and fine mesh screen 72. The armature center plate 65 serves primarily as a weight contributing element to the armature 6-3. This weight is ecessary in addition to the weight provided by the other components of the armature, in order to store and release sufiicient energy for operation at maximum design pressure and is necessary in connection in connection with a suitable combination of other elements in providing automatic adjustment of gap distance between the electromagnet pole and the armature base plate for different conditions of compressor back pressure loading. This thereby makes the compressor in its entirety compensating for back pressure changes. Additionally the armature center plate provides space for the large heads of bumpers 74.

The armature back plate serves primarily as a mass or weight contributing element in the armature, and this mass or weight serves the same purpose as it does in the center plate. Additionally, this back plate provides a place of attachment for the cup 69, and by means of a hole provided for that purpose also provides a centering and air entrance means for the cup. The back plate also serves to restrain the bumpers against motion in one axial direction.

Bumpers 74 are inactive, except for the minute incidental weight which they contribute to the armature assembly, during normal compressor operations. More specifically these bumpers are inactive during operation within the range of back pressure and of the line voltage for which the compressor is intended to be continuously design and construction of the compressor. This is true because the protruding ends of the bumpers extend be yond the face of the armature face plate a distance which isa few thousandths of an inch less than the minimum gap distance at the closest point of approach between the face plate and the poles of the electro-magnet during such normal operation. These bumpers provide a means to prevent the striking of the face of the electro-magnet upon the adjacent face of the armature face plate when the back pressure or the line voltage or both lies above that for which the compressor was intended to be continuously used. When such conditions arise, the electromagnet pole face and the armature face plate move near together than was intended at the time of the compressor desigm and construction, a condition resulting from the displacement of the armature toward the electro-rnagnet by the increased back pressure.

The bumpers thereby provide an inexpensive means to The holes 21 and 26 provide an opening through which air enters compression chamber. A valve seat which is adjacent to the said opening is slightly crowned as at crown 103. This slight crown provides, in conjunction with the valve disc, a very tight sealing means against air flow from within the compression chamber outwardly through the holes 102 during the compression cycle of the compressor. The inlet valve formed in this manner is self-cleaning. A pedestal 104 raises the valve seats sufficiently above the surrounding surface so that this surface will not interfere with the upper vaive disc operation. It will be noted that the valve disc retainer 70 has a slot 105 which extends radially across the crown in order that air can flow past the valve retainer. See Fig. 4. A valve retainer shelf 88 provides a place for attachment of the valve retainer 90 to the cup as shown in Fig. 8. The slot 105 also provides by which the valve disc by being folded upon itself, can be placed within its cell between the retainer and the cup. Additionally, the crowned annular projection which is integral with the valve retainer 70 and which is positioned adjacent to the valve disk 77 provides a means to position this disc adjacent'to or lightly pressed against the valve seat, while at the same time permitting this valve disc to move freely and easily away from its seat so as to permit almost unhindered flow of air between the disc and its seat on the inlet stroke of the compressor.

Valve disk 77 when used in the preferred construction of this invention, provides a valve action of great efiiciency and permits the use of relatively large, and therefore minimally restrictive, ports, while still maintaining tight seating and quick closing action. Additionally, this valve disk moves away from its seat easily and provides a large passage-Way so that air which passes from the outside past it and enter, the compression chamber is only slightly hindered, a condition which markedly improves the capacity and efiiciency of the compression chamber and of the compressor operation.

Several things contribute to the above action. 'In the preferred construction, the axial distance between the top of the crown of the valve seat and the top of the crown of the annular projection, is equal to, or a few thousandths less than the thickness of the valve disc. This valve disc may conveniently be approximately 0.008 inch thick made of neoprene rubber which is preferably electrically conductive rubber in order to dispose of static charges thereon. Restrained under the position of the said two crowns, it is the natural tendency of the valve disc to maintain its original flat shape and this causes the valve disc as used in the above discussed construction to be positioned adjacent or lightly pressed against its valve seat when no air is intended to be passed. This positioning of the disc against its valve seat is greatly advantageous in a device which operates at 120 cycles per second and which compresses only a small amount of air per cycle. When the valve components are arranged as above described, there is little or no escape of air.

from the compression chamber prior to the closing of the inlet valve. Yet, because the valve disk 77 is flexible and light, and because there is a space provided within the annular projection 78 for this. purpose, this valve 'moves quickly away from its seat, to a position causing only minor restriction to air flow during the inlet cycle. Also, by reason of its light we ght and resiliency, and additionally by reason of the fact that the motion of the restraining and positioning cell is at this instant being altered in a direction which assists in the action, this valve disc returns quickly and seats a most instantly at the start of the inlet cycle. The annular crown aids in the wide-opening of the valve. There is yet another advantage which valve disk 77 possesses when incorporated in the above construction. Because it is very light in weight, and thin, pliable and resilient, and. also because its surfaces are slick and because of the method of re-' straint, the valve disk will allow small particles of dirt of other foreign matter to pass between itself and its seat without interfering for an appreciable time with efficient valve action. This is very desirablebecause air compressors of the type described, one of the major causes of failure is faulty valve action resulting from dirt particles becoming permanently lodged or struck within the valve mechanism. It is to be recalled that the felt filter 71' is intended to stop only the coarsest of particles and to permit the passage of lesser particles. The primary air cleaning is done by the intercontainer sand fill. The felt filter is intended to retain only large stray bits of foreign matter which would clog the valve. It is not intended to be a cleaner, or it might itself become clogged and this is undesirable.

With respect to the discharge valve 87, the valve retainer shelf 88 provides a means for positioning the valve, and in conjunction with a valve retainer spring also provides a means for clamping the valve retainer into position axially. It will be noted that a pair of notches 106, 107 (see Fig. 5) is provided in the valve retainer plate of the discharge valve, and an off center hole 103 is provided inside the crowned projection of the aforesaid plate. These notches permit airflow when the valve is open, and the off center hole vents the space within the crown. Without this hole 108, air between the disc and the retainer would tend to oppose the opening of the valve by requiring compression of said air by the valve disc in order for the valve disc to move downward to open the valve.

The plenum chamber 86 provides 'a space for smoothing out pulsations in the air which leaves the compression chamber. Additionally it provides a compartment for holding and laterally positioning the discharge valve retainer spring 91. A valve port 109 through the plunger provides an opening through which air can leave the compression chamber. The enlarged entrance end 110 of this port provides good air fiow conditions and somewhat reduces noises. Valve seat 111, which is adjacent to the end of the valve port, provides in conjunction with the valve disc a very tight sealing means against air flow from the plenum space 86 back into the compression chamber during the intake cycle of the compressor. The pedestal 111 raises the valve seat sufiiciently above the surrounding surface so that this surface will not interfere with the proper valve disc operation.

The operation of the oscillatory compressor described above should already be evident. The cord is simply plugged into a source of alternating or interrupted direct current. The current energizes the electro-magnet and draws the armature toward it. This starts the intake part of the compressors cycle. Air which has entered the outer container around the cord and which has been cleaned by passage through the treated sand fill in the inter-container space, enters the inner container around the cord and thence enters the compression chamber through the inlet valve. The intercontainer sand fill acts as a low-velocity filter which effectively cleans the air. Any large particles of a size which would clog the valves, and which might accidentally have reached to compressor inlet are retained by the felt and the screen. During the inlet cycle, the discharge valve is closed.

The armature positioning springs are stretched by the energizing of the electro-magnet. When the electromagnet is de-energized, the springs pull the armature back. This is the compression cycle. The discharge valve opens, and the inlet valve closes. It will be noted that the frequency of compression is twicethe frequency of any alternating current which powers the compressor, because the electro-magnet isenergized by both positive and negativevoltages.

Compression waves of this frequency are quite audible, but the string mufiler, the intercontainer sand fill and the other suspension and sound deadening provisions effectively reduce this noise below audible levels.

13 Continued repetition of the above cycles provides a steady flow of compressed air. The compressor can scarcely be heard at all, even in the quietest room.

This invention also provides a compressor which, once assembled, is substantially self-adjusting for producing a steady output of compressed air over a wide range of back pressures. The effect of variation in back pressure is to change the rest position of the armature. For example, with a high back pressure, the armature will be moved upward in Fig. 1. This moves the armature closer to the electro-magnet, where the electro-magnet is more effective in stretching the positioning springs. Thus more work is done by the electro-magnet, and greater energy is imparted to the springs. The air can then be pumped against a greater back pressure, such as might result from placing the outlet tube in a deeper tank. The reverse is true for lesser back pressures, and the rest position of the armature will be lower in Fig. 1. So the device is self-adjusting over a wide range of back pressures, and the same compressor can be used to pump air into a wide range of tank depths, and through various types of difiusion devices such as stones and the like The compressor is protected against water damage by.

the expansible lozenge 120 of balsawood, bean, rice, or the like. Back fiow of liquid will expand the lozenge and close the discharge conduit. While the conduit will later have to be cleaned out and the lozenge replaced, still the pump will have been saved from great damage.

It will be observed that this compressor is quite etficient. One reason is that no damping is intended in the compression device. The suspension springs are just strong enough to support the mechanism in ordinary shipping and other handling. The structure attached to the yoke-like frame, and the armature are thus quite free to move relatively to each other. Substantially none of the energy supplied to the structure for causing this relative movement is wasted by damping either assembly. There is thus an almost optimum movement between the two, with the full fly-wheel effect of the armature utilized for compressing the fluid.

While this compressor has been principally described as an air pump for use in pumping air to aquariums, it is to be understood that it is useful for pumping any other compressible fluid, and for any other application where a source of such compressed fluid is desired.

This invention is not to be limited to the embodiment shown in the drawings and described in the description, which is given by way of example, and not of limitation, but only in accordance with the scope of the appended claims.

I claim:

1. An oscillatory compressor comprising: an electromagnet; a frame member attached to said electro-magnet; at least two spring means connected to said frame memher; an armature connected to said spring means; a cup attached to said armature for movement therewith; plunger means fixed to said frame; an annular U-shaped flexible seal ring having a pair of coaxial annular legs and a web portion connected between one end of the legs, means for connecting one of said legs to said cup and for connecting the other of said legs to said plunger so as to enclose a compression chamber of variable volume there-. in; an inlet valve for admitting air into the compression chamber; outlet means from said chamber; and a discharge valve interconnecting the compression chamber and the outlet means for fluid communication therebetween, said inlet and discharge valves acting as check valves to permit only intake to and discharge from the compression chamber, respectively, said armaturebeing disposed adjacent to and spaced from the electro-magnet for movement in a direction toward and away from the same, said spring means elastically restraining said armature for movement, whereby actuation and de-actuation of the electro-magnet pulls and releases the armature, re-

1dspectively,-thereby varying the volume of the compfession chamber and compressing air contained therein, and forcing said air into the outlet means.

2. An oscillatory compressor according to claim 1 in which the spring means comprises at least three coil springs aligned with the direction of oscillation of the armature, with the armature disposed between said springs and said electro-magnet, whereby actuation of the electro-magnet pulls the armature toward it and stretches the said springs, the springs being substantially identical, whereby the armature remains substantially parallel to said electro-magnet in the course of its oscillation.

3. An oscillatory compressor comprising: an electromagnet, a frame member attached to said electro-magnet; at least two spring means connected to said frame member; an armature connected to said spring means; a plurality of elastic bumpers secured to said armature and arranged to engage said electromagnet when said armae ture is within a predetermined distance of said electromagnet to thereby prevent said armature from contacting said electromagnet directly; a cup attached to said armature for movement therewith; a plunger attached to said frame means, said plunger including outlet means; an annular U-shaped flexible seal ring having a pair of co axial annular legs and a web portion connected between one end of the legs extending between the plunger and the cup for enclosing a compression chamber within the cup and permitting a change of volume of said compression chamber because of movement of the armature and cup toward and away from said plunger; an inlet valve carried by the armature for admitting air to the compression chamber; and an outlet valve interconnecting the compression chamber and outlet means for fluid communication therebetween, said inlet and outlet valves acting as check valves to permit only intake to and outlet from the compression chamber respectively, said armature being disposed adjacent the electro-magnet for movement in a direction toward and away from the same, said springing means being generally aligned with said direction whereby actuation of the electro-magnet pulls the armature toward said electro-magnet and deflects the spring means, thereby closing the outlet valve and opening the inlet valve for admitting air to the compression chamber, and whereby de-energizing the electro-magnet allows the spring means to move the armature and plunger away from the electro-magnet, thereby closing the inlet valve and opening the outlet valve and forcing fluid into the outlet means.

4. A pump assembly comprising: a container with an upperand lower end; a pair of first spring means attached to the inside of said upper end; an oscillatory pump comprising: an electro-magnet; a frame member attached to said electro-magnet; at least two second spring means connected to said frame member; an armature connected to saidsecond spring means; a cup attached to said armature for movement therewith; a plunger attached to said frame; flexible seal means interconnecting said plunger and cup to form a compression chamber of variable volume therebetween, the flexible seal means including an annular U-shaped flexible seal ring having a pair of co-v axial annular legs and a web portion connected between one end of the legs, one of the legs being connected to said armature for movement therewith and the other of said legs being connected to said plunger for movement therewith; an inlet valve for admitting air into the compression chamber; outlet means; and an outlet valve intel-connecting the compression chamber and outlet means for fluid communication therebetween, said inlet and outlet valves acting as check valves to permit only intake to and outlet from the compression chamber, respectively, said armature being disposed adjacent to and spaced from the electro-magnet for movement in a direction toward and away from the same, said spring means being generally aligned with said direction, whereby actuation of the electro-magnet pullsthe armature toward said electro-rnagnet and deflects the second spring means, thereby closing the outlet valve and opening the inlet valve for. admitting fluid to the plenum chamber, and whereby de-energizing the electro-magnet interrupts the said pull and allows the second spring means to move the armature and cup away from the electro-magnet, thereby closing the inlet valve, opening the outlet valve, and forcing fluid into the outlet means; said frame being connected to and suspended within said container by said suspension springs so as to be held out of contact with said container; and conduit means passing through said container and attached to said outlet means for conveying fluid under pressure from said pump.

5. A pump assembly comprising: an inner container with a side wall, and an upper and a lower end; a larger outer container with a side wall and an upper and a lower end, said inner container being within said outer container so as to form an inter-container space there between; porous material substantially filling said inter-container space; all walls and ends of the respective containers being thereby spaced from each other; a pair of first spring means attached to the inside of said upper end of'the inner container; an oscillatory pump comprising: an electro-magnet; a frame member attached to said electro-rnagnet; at least two second spring means conneeted to said frame member; an armature connected to said second spring means; a cup attached to said armature for movement therewith; a plunger attached to said frame; flexible seal means interconnecting said plunger and cup to form a compression chamber therebetween; an inlet valve for admitting air into the compression chamber; outlet means; and a discharge valve intercon mating the compression chamber and outlet means for fluid communication therebetween, said inlet and outlet valves acting as check valves to permit only intake to and outlet from the compression chamber, respectively, said armature being disposed adjacent to and spaced from the electro-magnet for movement in a direction toward and away from the same, said compression spring means being generally aligned with said direction, whereby actuation of the electro-magnet pulls the armature toward said electro-magnet and deflects the second spring means, thereby closing the outlet valve and opening the inlet valve for admitting air to the compression chamber, and whereby deenergizing the electro-magnet interrupts the said pull and allows the second spring means to move the armature and cup away from the electro-magnet, thereby closing the inlet valve, opening the outlet valve, a'nd forcing fluid into the outlet means; said frame being suspended within said container by said first spring means so as to be spaced out of contact with said inner conrainer; and conduit means passing through both of said containers attached to said outlet means for conveying fluid under pressure from said pump.

6. Apparatus according to claim in which said plunger includes the said outlet means, said cup and plunger being interconnected by the flexible seal so as to enclose said compression chamber, the relative excursion of the cup and plunger toward and away from each other creating variation in volume of the compression chamber.

7. Apparatus according to claim 6 in which the flexible seal comprises an annulus with a generally U-shaped cross-section having a. pair of spaced legs and a flexible portion inter-connecting the said legs, saidlegs being disposed outside of the compression chamber.

8. A pump assembly comprising: an inner container with a side wall, and an upper and lower end; alarger outer container with a side wall and an upper and lower end, said inner container being within the said container so as to form an inter-container space therebetween; a layer of sand in said inter-container space substanially filling the same, whereby all walls and ends in the respective containers are thereby spaced from each other; a set of compressible footings on the lower end of said outer containena layer of-plaster on the upper end of 1 said outer container; at flexible wrapping applied over the side wall and the plaster; a pair of first coil springs attached to the inside of said upper end of the inner container; an oscillatory pump comprising: an electromagnet; 21 frame member attached to said electro-magnet; said frame member being attached to the free ends ofthe said first coil springs; four second coil springs connected to said frame member; an armature connected to the said second springs; a cup attached to said armature for movement therewith; a plunger attached to said frame, said plunger including outlet means therein; a flexible seal extending between and interconnecting said cup and plunger, said cup and plunger thereby enclosing a compression chamber therebetween; an inlet valve for admitting air to the compression chamber; a discharge valve interconnecting the compression chamber and outlet means for fluid communication therebetween, said inlet and outlet valves acting as check valves to permit only intake to and outlet to compression chamber respectively, said armature being disposed adjacent to and spaced from the electro-inagnet for movement in a direction toward and away from the same, said first and second springs being generally aligned with said direc tion, whereby. actuation of the electro-magnet pulls the armature toward said. electro-magnet and deflects the second springs, thereby closing the outlet valve and openingvthe inlet valve for admitting air to the compression chamber, and whereby de-energizing the electro-magnet interrupts the said pull andallows the second springs to move the armature and cup away from the electro-magnet thereby closing the inlet valve, opening the outlet valve, and forcing fluid into the outlet means; and a conduit means passing through both of said containers attached tosaid outlet means for conveying fluid under pressure from said pump.

9. A pump assembly according to claim 8 in which thearmature'comprises three magnetic plates all of said plates having a central hole'therethrough, the plate nearest the electro-magnet having a pair of holes of afirst diameter, and a second of said armature plates adjacent said first plate having aligned holes of greater radius; rubber bumpers: held in the said second holes by the said first plate and protruding beyond said first plate toward the said armature to act as bumpers; a filter means in said central holes; said inlet. valve being held to said cup and comprising a plate having a crown with an opening therethrough, said inlet valve including a flat flexible disc of electrically conductive material.

10. Apparatus according to claim 9 in which said outlet means includes an outlet chamber in said plunger, a valve retainer having an annular crown and an opening therethrough, within said crown, a flexible flat disc adjacent to the said retainer, and spring means biasing the retainer toward thesaid flexible disc.

11. Apparatus according to claim 10 in which the said disc is made of electrically conductivematerial.

12. Apparatus according to claim 11 in which the conduit means is re-inforced' by a coil spring positioned therewith, and in which a muflier is provided comprising a piece of string inserted therein.

13. Apparatus according to claim 12 in which the flexible seal is generally U-shaped, having legs and a central flexible section, the outer leg being cemented to the cup, and the inner leg being cemented to the plunger, and in. which a snap ring is inserted between the said legs for further holding the flexible seal against the cup, said legs being disposed outside the compression chamber.

14. Apparatus according to claim 13 in which a plug of dry material which is expansible by contact with liquids, of lesser dimensions than said conduit when said plug is dry, is provided in said conduit, whereby back flow of liquid into the pump is prevented when the liquids contact, wet and expand said plug to seal said conduit.

15-. In an oscillatory compressor of the class described, the combination which comprises an electro-magnet, a

frame member secured at one end to the electro-magnet, an armature, first. second and third helical springs, first, second, third, fourth, fifth and sixth spring fastening members, the first, second and third fastening members being secured between the armature and one end of the first, second and third springs respectively, the fourth, fifth and sixth fastening members being secured between the other end of the frame member and the other end of the first, second and third springs respectively, the fastening members being arranged to prevent any one of the springs from completely closing when the armature is moved relative to the electro-magnet in a direction to compress the springs, whereby a force exceeding that required to compress the springs beyond their elastic limit may be applied between the armature'and the frame member in a direction to compress the springs without stressing the springs beyond their elastic limit, a chamber including an inlet and an outlet disposed between the armature and the other end of the frame member, a flexible seal disposed adjacent the inlet and secured between the armature and the other end of the frame member and means including the seal for pumping fluid from the inlet to the outlet of the chamber in response to movement of the armature in a direction toward and away from the electro-magnet.

16. The combination as defined in claim 15 wherein each of the spring fastening members is a cylindrical stud having an elongated boss at one end thereof which is adapted to be riveted to the armature or frame member, an externally threaded central portion which is arranged to receive one end of one of the springs, and a cylindrical stem having a smaller diameter than the cen tral portion at the other end, the stem being arranged to extend longitudinally into one of the springs and engage the stern of another stud secured to the other end of said one spring to limit the movement of the armature relative to the other end of the frame member.

17. In an oscillatory compressor the combination which comprises a frame member, an electro-magnet secured to the frame member, an armature disposed adjacent the electro-magnet, spring means connected between the armature and the electro-rnagnet to bias the armature away from the electro-magnet, whereby energizing the electro-magnet pulls the armature toward the electromagnet and de-energizing the electro-magnet causes the armature to move away from the electro-magnet, an annular U-shaped flexible seal ring having a pair of coaxial annular legs and a web portion connected between one end of the legs, and means for securing the seal ring between the armature and the frame member to form a compression chamber therebetween, the means for securing the seal ring being arranged to place the web portion in compression to cause the seal ring to have an overcenter action.

18. The combination as defined in claim 17 wherein the last named means includes a cup attached to the armature for movement therewith, a plunger attached to the frame member, the seal ring being secured between the cup and the plunger for enclosing a compression chamber within the cup and permitting a change of volume of the compression chamber with movement of the armature and cup toward and away from the plunger, the plunger including outlet means, and valve means for selectively admitting air into the compression chamber and for selectively interconnecting the compression chamber with the outlet means whereby movement of the armature toward and away from the electro-magnet will pump fluid to the outlet means.

19. The combination as defined in claim 17 wherein the legs of the seal ring increase in thickness with increasing distance from the web portion.

20. The combination as defined in claim 19 wherein the outer surfaces of the legs are arranged normally to diverge from each other as the legs extend from the web portion and wherein the means for securing the seal ring between the armature and the frame member is arranged to force the outer surfaces of the legs into a parallel relationship to place the web portion in compression.

21. The combination as defined in claim 19 wherein the outer surfaces of the legs are arranged normally to diverge from each other as the legs extend from the web portion, the web portion having one thickness adjacent the legs and a lesser thickness in the central portion thereof, and wherein the means for securing the seal ring between the armature and the frame member is arranged to compress the web portion and to force the outer surfaces of the legs into a parallel relationship to cause the web portion to assume a convex shape extending generally away from the frame member.

22. A compressor assembly comprising a container; an electro-magnet disposed within the container; a frame member attached to the electro-magnet, an armature disposed within the container and adjacent the electro-magnet for movement toward and away from the electro-magnet in one direction, first spring means connected between the armature and the frame member to bias the armature away from the electro-magnet, second spring means connected between one side of the container and the frame member to bias the frame member and the electro-maguet away from said one side of the container, the first and second spring means being generally aligned with the direction of movement of the armature whereby each of the first and second spring means absorbs energy when the electro-magnet is energized to move the electro-magnet and the armature toward each other and the first and second spring means dissipate the absorbed energy by moving the electro-magnet and the armature away from each other when the electro-magnet is de-energized to thereby balance the forces created between the armature and the electro-magnet and substantially isolate the container from said forces, means including a flexible seal connected between the armature and the frame member for forming a compression chamber having an inlet and an outlet, and means for selectively closing the inlet and the outlet to cause fluid to be pumped from the inlet to the outlet in response to movement of the armature and the electromagnet relative to each other.

23. A pump assembly as defined in claim 22 wherein the first spring means comprises at least three helical springs and the second spring means comprises at least two helical springs.

24. The pump assembly as defined in claim 22 wherein said means for selectively closing the inlet and the outlet of the compression chamber includes a valve disc composed of an electrically conductive resilient material.

25. A pump assembly as defined in claim 22 including a tank of liquid and a conduit secured at one end to the outlet of the compression chamber, the other end of the conduit being disposed within the tank of liquid and a plug of dry material disposed within the conduit, the plug being expansible by contact with liquids and of lesser dimensions than the conduit when the plug is dry whereby liquid flowing into the conduit from the tank will wet and expand the plug to seal the conduit and backfiow of liquid into the compressor will be prevented.

26. An oscillatory compressor of the class described including a frame member, an electro-magnet secured to one end of the frame member, an armature disposed adjacent the electro-magnet, first and second helical springs, first, second, third and fourth spring fastening members, the first and second fastening members being secured between the other end of the frame member and one end of the first and second springs respectively, the third and fourth fastening members being secured between the armature and the other end of the first and second springs respectively, the first and third and the second and fourth fastening members being arranged to cooperate with each other to limit the movement of the armature with respect to the other end of the frame member to prevent complete compression of the first and second springs whereby the armature may be urged toward the other end of the frame member with a force much greater than the force of compression of the first and second springs without damagingthe. springs, means including a flexible seal connected between the armature and the frame member for forming a, compression chamber having an inlet and an outlet and meansfor selectively closing the inlet and the outlet to cause fluid to be pumped from the inlet to the outlet in response to movement of the armature and the elect'ro-magnet relative to each other.

27'. In an oscillatory compressor assembly comprising a frame member, an electro-magnet secured to the frame member, an armature disposed adjacent to the electromagnet, first and second helical springs, first, second, third and fourth spring.fastening members, the. first and second fastening members being secured between the frame. member. and one end of the-first andsecond springs, respectively, the. thirdand. fourth fastening members being secured between the armature and the other end of the first and secondsprings,.respectively, the first and third and the second, and fourth fastening members being arranged to cooperate with. each other to limit the movemeritv of the armature relative to the frame member to prevent complete compression of the first and second springs. so that a force exceeding. that required to compress the springs beyond the elastic limit thereof may be, applied between the armature and the frame member.

without stressing the springs beyond said elastic limit, a flexible seal connected between the armature and the. framemember for forming a compression'chamber having; an inlet andtan outlet, and meansfor selectively: closing; the inlet and.the=outlct to cause fluid to be pumped from the. inletto theaoutlet in response to relative movement between the armature and the electro-magnet.

References Cited in the file of this patent- UNITED STATES PATENTS 1,964,687 May June 26, 1934 1,978,866 Konig Oct. 30, 1934 1,996,160 Konig Apr. 2, 1935 2,076,665 Noble -Apr. 13, 1937 $233,082 Kucher Feb. 25, 1941 2,261,648 Goldstein Nov. 4, 1941 2,410,984. Lawless Nov. 12, 1946 2,420,929 Buflingtonet al May 20, 1947' 2,470,925 Frederickson May 24, 1949 2,490,505 Benjamin Dec. 6, 1949 2,598,609 Samuel 2 May 27,1952 2,627,811 Van'Ryan Feb. 10, 1953 2,706,795 Dickey Apr. 19, 1955 2,845,080 Kraft July 29, 1958 FOREIGN. PATENTS 821,000 Germany Nov. 15, 1951 UNITED STATES PATENT OFFICR CERTIFICATION OF CORRECTION Patent No. 2,961,149 Not ember .22, 1960 Robert R. Hull It is hereby certified that error appears in the above numbered pat ent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 54, for "manually" read manual line 68, for "supply" read support same line 68, for M "normally" read normal column 4, line 33, tor "shapplng read shipping lines 45 and 46, for "materall" read material line 72, for "said" read sand column 5, line 28, for "42" read 43 line 32, after "length" insert of line 64, after "out" insert of line 75, for "consists" read consist column 10, line 23, strike out "in connection", second occurrence; column 12, line 6, for "struck" read .stuck Signed and sealed this 6th day of. June 1961,

(SEAL) Attest:

ERNEST W. SWIDER DAVID L, LADD Attesting Officer Commissioner of Patents 

